This invention relates to a hot-melt adhesive line and an article of manufacture including the same to provide reinforcement, a tear line and/or seal line for packaging wherein the hot-melt adhesive line is comprised essentially of at least one bundle of fibrous strands and a sufficient amount of hot-melt adhesive for interstrand adhesion and for a compacted coating on the bundle of strands to form a predetermined shape to the line to undergo lateral spreading when reheated and under an applied force.
While not so limited, the hot-melt adhesive line of the present invention is particularly useful to reinforce and/or strengthen one or more walls of a packaging container and useful to form a package seal element and/or a tear element for opening a packaging container. Corrugated cartons used for packaging are cumbersome to reinforce from the standpoint of both expense and effectiveness. Stressed areas in a corrugated carton are usually reinforced by using heavy liners or a multi-wall construction. Not only are the stressed areas reinforced, but also the entire carton. As a result, unnecessary bulk and weight are added to the container. Such measures for reinforcing stressed areas of a carton also increase the cost without a significant improvement to the wet strength, bulge resistance, durability and loading strength.
To overcome these shortcomings and disadvantages, the present invention provides a hot-melt adhesive line and an article of manufacture including such line for packaging which dispenses with the need for expensive paper stock by utilizing high tensile strength filaments and hot-melt adhesive to add reinforcement to a corrugated container or the like either during the manufacturing process for the container or after manufacturing by the sample addition of heat to activate the thermoplastic adhesive for bonding after lateral spreading under an applied force at the desired site. In this way, reinforcement is readily achieved at critical stress points to adapt the carton for specific needs. Moreover, a package seal line is easily added and the same line may be used as reinforcement to absorb and spread compressive loads, shocks and stresses to enable the use of lower-weight liners without reducing the performance of the carton.
In copending application Ser. No. 13,577, assigned to the Assignee of this invention, there is disclosed a coating method that is used to produce the line of the present invention since the method provides a high production capacity and capability to produce the hot-melt adhesive line. The line has a compacted and shaped adhesive coating tightly adhered to fibrous yarn. Because of the nature of the product, fibrous yarn must be fed through a coating line at an economically feasible speed. However, the speed at which the coating process is carried out is dependent on variables including the type of yarn, material of the yarn and properties of the selected adhesive. This coating method is based on the discovery that the yarn must be preconditioned with respect to tension and cross-sectional shape immediately before coating with adhesive and within the very short residence time of the yarn in a bath of hot-melt adhesive. Absent such preconditioning of the yarn, there is an immediate stripping of any adhered coating in the bath because of the speed at which the yarn is pulled through the bath.